The biochemical composition of a cell is a complex mix of biological molecules including, but not limited to, proteins, nucleic acids, lipids, and carbohydrates. The composition and interaction of the biological molecules determines the metabolic state of a cell. The metabolic state of the cell will dictate the type of cell and its function (i.e., red blood cell, epithelial cell, etc.). Tissue is generally understood to mean a group of cells that work together to perform a function. An organ is generally understood to mean a group of tissues organized to perform a function. Raman spectroscopic techniques provide information about the biological molecules contained in cells, tissues, and organs and therefore provide information about the metabolic state. As the cell's, tissue's, or organ's metabolic state changes from the normal state to a diseased state. Raman spectroscopic techniques can provide information to indicate the metabolic change and therefore serve to diagnose and predict a disease state and a clinical outcome in a patient.
Organ transplantation is a final alternative treatment in several diseases including but not limited to kidney failure, heart failure, lung failure, liver failure, tendon and ligament failure, corneal clouding, and lens failure, among others. There are also diseases and conditions where the treatment includes transplanting bone, bone marrow, skin, hematoetic cells, or other cells.
When an organ, tissue, or other material is transplanted into a host, rejection of the material by die host is always possible. Rejection of transplanted material can occur either acutely or chronically. In the case of acute rejection, there is a relatively rapid reaction between the transplanted material and the cells and tissues of the receiving patient. In the case of chronic rejection there is a slower progression of reaction to the transplanted tissue. Both forms of rejection can occur within the context of different transplanted organs and occur by complex physiological pathways which are not completely understood.
In the specific case of kidney transplant, approximately 30% of transplanted kidneys go through a process of chronic rejection. Such rejection may occur days, weeks or months after the transplant has taken place. There is no known way to predict the development of chronic rejection in the case of a specific kidney, donor, or recipient.
Raman spectroscopy holds potential for the detection of various types of incipient or occurring rejection. Because Raman spectroscopy is based on irradiation of a sample and detection of scattered radiation, it can be employed non-invasively to analyze biological samples in situ. Thus, little or no sample preparation is required. Raman spectroscopy techniques can be readily performed in aqueous environments because water exhibits very little, but predictable, Raman scattering. It is particularly amenable to in vivo measurements as the powers and excitation wavelengths used are non-destructive to the tissue and have a relatively large penetration depth. Therefore, it is desirable to devise methodologies that use Raman spectroscopy and imaging techniques to differentiate various cell types, to classify disease states of biological samples under investigation, and to predict clinical outcomes in patients.